How to calculate the heat loss of a family house?

Have you planned a renovation of your family house? Is everything at home out of date, from the floors and kitchen units to the heating? This is where we hit on the issue that keeps you up at night. How can you best prevent heat loss?

If you have decided to insulate your house or install heating, the most important figure is heat loss. Heat loss is the amount of heat that escapes from the house to the outside. So it does not really matter whether the heat is escaping through the walls, the windows or ventilation.

In the Czech Republic, heat loss is usually calculated for a temperature of -15°C. In mountain areas, however, this temperature is somewhat more severe, down to -18°C. In towns and warm areas, on the other hand, which is logical, the temperature is around -12°C.

On the other hand, you may be thinking that in winter temperatures are often much lower than -15°C. But there is an explanation for this too. Most houses usually have some ability to store heat, so they can cope with short drops in temperature below the design value. The opposite of heat loss is heat gain, which happens when sunlight falls through the windows into the interior of your house and warms up the rooms.

How to prevent heat loss?

When it comes to heat loss, all advice is costly, but this is probably the most basic. Buy new windows or a new front door. Invest in the roof or the floor. Or buy dampers for unused chimneys and get net curtains or drapes. If you live in a flat, you can glaze your balcony. These measures will help you prevent heat loss or remove it altogether.  

How much does heating cost per year?

The most common question about heat loss is how much we will actually pay for energy. For some types of energy we pay a monthly fee, but there are also various tariffs and the like. Given that energy prices change all the time, it is a good idea to check whether a given price still applies.

How to calculate your house’s heat loss?

Calculating your house’s heat loss is not that simple. It is always better to turn to a building designer or an energy specialist. They should carry out a calculation for you with the help of specialised software.

If you only need a rough calculation, try the TZB-Info portal, where an online tool will give you an estimate. The system is designed for people interested in a grant from the New Green Savings programme (Nová zelená úsporám). The Tepelná technika 1D program can also be useful, as it calculates a number of things based on the parameters you enter and points you in the right direction. If you have decided to apply for a grant, bear in mind that the form is not entirely easy to fill in. You also need to know a whole range of information about your building:

• Building volume
• Total area of the family house
• Total floor area
• Permanent heat gain
• Type of masonry (external walls, internal walls and partitions)
• Thermal transmittance of the windows
• Roof structure, including the thickness and type of insulation
• Type and thermal transmittance of all doors, and much more

Enter the values as accurately as possible. If you do not know some of them, use the help.

You can then calculate heat loss in two ways:

• The envelope method for the whole building
• In detail, room by room

If you have decided to keep your existing radiators, it is enough to calculate heat loss using the envelope method.

A big advantage of calculating annual heat demand from heat loss is that you immediately find out what output you need to cover the heat loss. This means how to size the boiler and how much energy you will use. In addition, such calculations work well for old uninsulated houses, as heat loss through transmission predominates in them.

Do not be afraid to contact experts

You are certainly not alone if you turn to an expert for a heat loss calculation. As we have already mentioned, it is best to contact a building designer or a specialist. However, they must have specialised software and plenty of experience with similar cases. The final price of a heat loss calculation depends on the size of the building plus the cost of the work.

If, after reading our article, you have decided to buy a cooperative flat instead, take a look at our other articles, such as how to get rid of fruit flies or how to change the pace of your life.